The invention is in the field of mechanical engineering and relates to conveying devices for fluids, in particular for liquids.
Such conveying devices have become known in the form of different kinds of pumps in the most varied of embodiments. Pumps are of particular interest at this point which can be manufactured in such constructions that they can be used for more sensitive fluids, in particular fluids having macromolecules. A specific group among such pumps is represented by the fluid pumps which can be used for medical application purposes and which can be manufactured in small constructions. Such pumps can also be used in micro constructions, for example, for conveying the body's own fluids, or biocompatible fluids, for example as heart pumps for conveying blood.
In the conveying of such sensitive fluids such as blood which have large and sensitive molecules, for example, which satisfy biological functions and which therefore also may not be damaged at the microscopic level, care must be taken that the mechanical effect on the fluid by pressure maxima, shear forces and accelerations is limited as much as possible.
Axial flow pumps have in particular become known in this connection, for example, for the conveying of blood which have a rotor which rotates about a longitudinal axis, which has impeller blades and which continuously conveys blood in the axial direction.
Since a specific problem for the use of such pumps in the inside of the body comprises the fact of providing them, on the one hand, with sufficient conveying capacity, and, on the other hand, however, of configuring the construction size so that they can be introduced through a blood vessel, some of the challenges for such pumps comprise the fact of configuring them from a construction aspect so that they are radially compressible and expandable again for operation in the body.
A compressible rotor of this kind is known, for example, from U.S. Pat. No. 6,860,713. Another rotor is known from U.S. Pat. No. 7,393,181 B2. In the known solutions, the rotors are compressible and expandable either due to the elasticity and deformability of the material or on the basis of mechanically movable constructions.
It is unavoidable in this respect that a certain construction effort is exerted to ensure the compressibility of such a pump despite a corresponding reliability and conveying capacity. It must moreover be ensured that large shear forces which can damage sensitive fluids do not arise due to too high a rotational speed of the rotor or due to unfavorable geometrical shapes of impeller blades. In addition, care must be taken that pressure differences within the geometry of such a conveying device, on the one hand, and over the course of time, on the other hand, are kept within tight limits.